1. Field of the Invention
The present invention relates to a RF tuning element or RF probe used in electromechanical slide-screw tuners for RF impedance synthesis. The technique of subjecting DUT to variable load impedance or variable source impedance with corresponding load slide-screw tuner and source slide-screw tuner, commonly referred to as “load pull”, is used to test transistors for amplifier, oscillator or frequency multiplier applications.
2. Description of Prior Art
RF probes for electromechanical tuners have been very conservative since their invention by Julius LANGE. According to FIGS. 1 & 2, a RF probe consist of a parallelepipedic bloc (1) having a curved slotted portion in relationship with the transmission line, inserted into a transmission line, including, but not limited to slabline, comprising an inner central conductor (104) and an outer grounded conductor (103). By moving this RF probe (1) with (100) up and down, i.e. toward and outward the central conductor (104) according to arrow (101), one can modify the amplitude of the VSWR (Voltage Standing Wave Ratio), while moving the RF probe (1) with (100) in parallel with the central conductor (104) according to arrow (102), one can modify the phase of the VSWR. One improvement has been disclosed in U.S. Pat. No. 6,980,064 issued to Philippe Boulerne on Dec. 27, 2005, incorporated herein by reference, which discloses a corrugated probe, which purpose is to increase the amplitude of the VSWR range. FIG. 3 discloses a corrugated probe (2) with a single corrugation, FIG. 4 discloses a corrugated probe (3) with two corrugations and FIG. 5 discloses a corrugated probe (4) with three corrugations. U.S. Pat. No. 6,980,064 does not disclose the possibility to use exiting probes and make a single RF tuning element from existing RF probes. Also U.S. Pat. No. 6,980,064 does not disclose the possibility to modify the lengths of the slots making the corrugations.